Understanding the core density profile in TCV H-mode plasmas

摘要

Results from a database analysis of H-mode electron density profiles on theTokamak \`a Configuration Variable (TCV) in stationary conditions show that thelogarithmic electron density gradient increases with collisionality. Bycontrast, usual observations of H-modes showed that the electron densityprofiles tend to flatten with increasing collisionality. In this work it isreinforced that the role of collisionality alone, depending on the parameterregime, can be rather weak and in these, dominantly electron heated TCV cases,the electron density gradient is tailored by the underlying turbulence regime,which is mostly determined by the ratio of the electron to ion temperature andthat of their gradients. Additionally, mostly in ohmic plasmas, the Ware-pinchcan significantly contribute to the density peaking. Qualitative agreementbetween the predicted density peaking by quasi-linear gyrokinetic simulationsand the experimental results is found. Quantitative comparison wouldnecessitate ion temperature measurements, which are lacking in the consideredexperimental dataset. However, the simulation results show that it is thecombination of several effects that influences the density peaking in TCVH-mode plasmas.